Holographic Sonar Cryptography

Atomic Snarl writes: "New Scientist.com has this story on how to encrypt a underwater sonar message using multiple sound path timing. By detecting and adapting for the current variations on underwater sound channels, the transmitted message can be received intelligibly only at a single point. This holographic approach suggests a method of web encryption using multiple hop paths and ping times to create a message which can only be decoded when received at a specific target node!"

Comments

Re:Doubt that it would be useful..

[MrFredBloggs]

Its been done. Read `the cuckoos egg` by clifford stoll. They worked out the hacker was in Germany via a similar method to the one you described.

Re:Radio?

[jlseagull]

i've done some work on this. this is indeed possible, though the radios on both ends need high sample rates if the communication will be recieved over short distances, which isn't practical on 802.11b cards - the sample rates are in the Gs/s range. in addition, the signal environment that 802.11b operates in is highly variable, and subject to reflective and refractive variations in power on the order of +/-3dB over 10us. Phase variations can be as large as 1000%(that is, 10 times as long as the wave itself) over the same timescale, making phase correlation and interferometrics totally useless. Something as simple as a fan running can perturb the signal environment on the other side of the building to this degree(believe me, we tried it). it might, *might* work over larger static environments like a city or a mountain range, but 802.11b isn't spec'd for that kind of range. so the short answer is, no.